1. Field of the Invention
The preset invention relates to a cooperation system, in which a robot is operated with respect to a machine tool.
2. Description of the Related Art
When a robot is operated with respect to a machine tool, the robot may carry out an operation such as exchanging a tool, cleaning chips, checking an inside of the machine tool, etc., as well as handling an object to be processed. When the operation of the robot is only handlings of an object, it is normal that a plurality of (normally, three or four) teaching points on the object in the machine tool are obtained, and a coordinate transformation matrix from a robot coordinate system to an object coordinate system (or a machine coordinate system) is calculated, by using the position of a tool center point of the robot.
For example, JP S59-177607 A discloses an automatic programming method for automatically generating a robot program from a program of a machine tool, by connecting the machine tool to a robot and by using a conversion equation between a coordinate system with respect to the robot and a coordinate system with respect to the machine tool.
JP H05-212652 A discloses a precision processing machine having a process zone and a measurement zone, and having a first calculation means for calculating a coordinate transformation matrix based on measurement data; a second calculation means for converting the measurement data by using the calculated transformation matrix; a judgment means for judging shape accuracy of calculated shape data; a correction means for automatically correcting NC data; and a process execution means for carry out processing again based on the corrected NC data.
JP H05-324034 A discloses a method for controlling a robot, in which a supervisory computer of a machine tool for carrying out NC control transmits motion control data to a robot controller, so that the robot exchanges or moves a workpiece or a tool of the machine tool.
JP 2008-152733 A discloses an offline programming device for generating an operation program, in which the position and orientation of an object on a machine tool during handling operation are calculated based on a command for specifying the position of the object in a work processing program given to the machine tool, and the position and orientation of the robot are calculated during the handling operation based on a predetermined positional relationship.
JP H11-509928 A discloses a device and a method for generating a three-dimensional model of an object, by using a probe attached to a robot so as to obtain a coordinate system of the robot relative to a robot coordinate system. This document also describes that the three-dimensional model of the object is generated by obtaining a coordinate value of the object based on a plurality of images obtained by moving a camera attached to a front end of the robot and capturing the object by the camera.
JP 2009-279677 A discloses a robot controller configured to automatically correct a teaching position by moving a robot or an object to be worked so as to obtain a desired positional relationship, without calibrating a measurement device such as a camera.
In the prior art, the coordinate transformation between a robot coordinate system and a machine coordinate system is mainly used for handling an object to be processed. For example, JP S59-177607 A discloses a method using the robot so as to easily generate a handling program of the object to be processed by the machine tool, and JP H05-324034 A discloses a method for easily commanding the robot by using the supervisory computer, so that the robot carries out handling of the object to be processed by the machine tool and attachment/detachment of the tool. However, although the coordinate transformation is carried out in JP S59-177607 A or JP H05-324034 A, a concrete method for obtaining a means for the coordinate transformation is not described in these documents.
In JP H05-212652 A, an amount of processing of the machine tool is corrected by using the difference between a measured surface of an object to be processed and an ideal curved surface, and the coordinate transformation from a coordinate system defined corresponding to the measurement device and a coordinate system defined at a determined position of the machine tool. However, a concrete method for obtaining a means for the coordinate transformation from the coordinate system regarding the measurement device to the coordinate system regarding the machine tool is not described in this document.
In JP 2008-152733 A, in order to obtain a coordinate system common to the robot and the machine tool, a position detector is attached to a front end of the robot, a target to be detected is attached to a table of the machine tool, the position of the front end of the robot is fixed, and the position of the target is detected at the different three positions. Concretely, first, a reference position of the target is determined, and the target is detected at the reference position. Second, the table is moved in the direction of a reference axis, and the target is detected. Third, the target is moved in the direction of a different reference axis, and the target is detected. Based on a coordinate transformation matrix calculated from the obtained three measurement values and a simulation result of by an offline simulation device, the robot is calibrated. However, in this method, it is necessary to prepare a high-precision three-dimensional CAD model used in the offline simulation device. Further, a positional error between the actual robot and the actual machine tool may be included in the calculation of the offline simulation device.
Further, in the method of JP H05-324034 A or JP 2008-152733 A, it is necessary to use the supervisory computer or the offline simulation device, as well as the robot and the machine tool, whereby a cost of a factory including the same may be high.
In addition, when the task of the robot for the machine tool includes an operation other than the handling of the object to be processed, it is necessary that the robot can access or approach another area of the machine tool, as well as the object. In such a case, there are many limitations in the location of the robot.
As described above, when the task of the robot includes various operations other than the handling of the object to be processed and these operations should be automated, it is insufficient that the robot merely has coordinate information for the operation near the object.